¹³⁷Petrie, George. "On the History and Antiquities of Tara Hill." The Transactions of the Royal Irish Academy, vol. 18, 1839, pp. 138-9.
"The Monuments of Cu and Cethen lie on the Leither (slope) in the vicinity of Rath riogh to the west. There are two stones here; the one, the monument of Cu, the other, that of Cethen. So that it has become a common saying, 'They have acted like Cu and Cthen,' i.e. Cu slew Cethen, Cormac’s butler, in the middle of the house; and he passed directly under the height of Temur to the west, where he was overtaken and killed by the brother of him whom he had slain."